This invention relates to electrical printed wiring circuit boards and more particularly to apparatus for their fabrication.
Printed wiring circuit boards have long been known in the art as providing a highly advantageous means for organizing and supporting electrical conductors and circuit components. Such boards are typically formed as an epoxy glass laminate and have wiring printed thereon by a number of known methods in patterns as dictated by circuit functions. In many cases, the boards are mounted in edge connectors which also provide electrical interconnections with terminations of the wiring carried on the board. The connectors generally provide spring-type contacts between the fingers of which the board is inserted, the connector contacts making separable connection with corresponding terminations of the board wiring. These connections are not directly made with the copper printed conductors themselves, however. In order to ensure a low resistance connection which is also wear resistant, the conductor terminations are provided with gold-plated contact surfaces. Such gold platings at the contact areas of the conductors may be affixed thereon by a number of known methods, each of which involves a loosely controlled and time-consuming process including cleaning and preparing the copper surface and other manual steps. Further, at present, the plating takes place during the formation of the printed conductors themselves. As a result, the plated contact surfaces must be protected against all of the hazards of circuit board assembly. The plated surfaces are thus subject to possible abrasion, warping, solder contamination, and the like. Any defects in the precious metal plating may require the rejection of a circuit board when the remainder of the board circuitry is acceptable. Conversely, acceptable contact platings may be lost when other parts of the board prove defective.
It is accordingly one object of this invention to facilitate and reduce the cost of applying precious metal contact surfaces to printed wiring circuit boards.
Another object of this invention is to provide new and novel apparatus adapted for the application of precious metal contact surfaces to printed wiring circuit boards.
It is also an object of this invention to provide apparatus as characterized in the foregoing which may be automatically controlled to reduce to a minimum the number of manual steps required in the contact surface application operation.
A further object of this invention is to ensure the quality of precious metal contact surfaces of printed wiring circuit boards.